Pharmacogenetics of analgesic drugs

Effects of pharmacogenetic profiles on pediatric pain relief and adverse events with ibuprofen and oxycodone

Introduction

Individual genetic variation may influence clinical effects for pain medications. Effects of CYP2C9, CYP3A4, and CYP2D6 polymorphisms on clinical effectiveness and safety for ibuprofen and oxycodone were studied.

Objective

Primary objectives were to AU2 evaluate if allelic variations would affect clinical effectiveness and adverse events (AEs) occurrence.

Methods

This pragmatic prospective, observational cohort included children aged 4 to 16 years who were seen in a pediatric emergency department with an acute fracture and prescribed ibuprofen or oxycodone for at-home pain management. Saliva samples were obtained for genotyping of allelic variants, and daily telephone follow-up was conducted for 3 days. Pain was measured using the Faces Pain Scale-Revised.

Results

We included 210 children (n = 140 ibuprofen and n = 70 oxycodone); mean age was 11.1 (±SD 3.5) years, 33.8% were female. Median pain reduction on day 1 was similar between groups [ibuprofen 4 (IQR 2,4) and oxycodone 4 (IQR 2,6), P = 0.69]. Over the 3 days, the oxycodone group experienced more AE than the ibuprofen group (78.3% vs 53.2%, P < 0.001). Those with a CYP2C9*2 reduced function allele experienced less adverse events with ibuprofen compared with those with a normal functioning allele CYP2C9*1 (P = 0.003). Neither CYP3A4 variants nor CYP2D6 phenotype classification affected clinical effect or AE.

Conclusion

Although pain relief was similar, children receiving oxycodone experienced more AE, overall, than those receiving ibuprofen. For children receiving ibuprofen or oxycodone, pain relief was not affected by genetic variations in CYP2C9 or CYP3A4/CYP2D6, respectively. For children receiving ibuprofen, the presence of CYP2C9*2 was associated with less adverse events.

Prescription Patterns of Analgesic Drugs in the Management of Pain Among Palliative Care Patients at a Tertiary Hospital in Oman: A Retrospective Observational Study

Objectives Analgesic drugs are commonly used to alleviate the pain experienced by palliative care (PC) patients. Thus, we sought to determine the prescription patterns of analgesic drugs in the management of pain among haematology and oncology palliative care patients at Sultan Qaboos University Hospital (SQUH) and then see if they were following the World Health Organization (WHO) guidelines. Methods A retrospective observational cross-sectional study was conducted, and adult PC patients prescribed analgesics for pain relief between January 2018 and January 2021 at SQUH constituted the sample. Data were collected from patients' electronic medical records using the SQUH TrakCare system. The data was then presented descriptively using graphs and tables. Results Data from 200 PC patients were analyzed. Breast cancer was the most common malignancy, with 73 (36.5%) patients diagnosed with it. Severe pain was the most reported degree of pain, with exactly 100 (50.0%) patients experiencing it. More patients experienced mild pain than moderate pain. Opioids were the most prescribed analgesics, followed by analgesics and antipyretics, anticonvulsants, and finally non-steroidal anti-inflammatory drugs (NSAIDs). Paracetamol was the most prescribed analgesic for pain overall, with 127 (63.5%) patients utilizing it. For severe pain, morphine was the most prescribed analgesic, with 65.0% of patients using it. Fentanyl and pregabalin, the strongest two analgesics, increased in prescription for severe pain compared to mild and moderate pain, with both being prescribed to 23.0% of patients suffering from severe pain. The oral route of administration was the most prescribed, with 128 (64.0%) utilizing it. Conclusion This study showed the prescription patterns of analgesic drugs for palliative care patients at SQUH. The findings were similar to those of other studies, though there were some differences. The prescription patterns of analgesic drugs prescribed for the various pain levels among PC patients were found to be in accordance with the WHO guidelines.

Non-opioid analgesics for procedural pain in neonates

BACKGROUND

Neonates are an extremely vulnerable patient population, with 6% to 9% admitted to the neonatal intensive care unit (NICU) following birth. Neonates admitted to the NICU will undergo multiple painful procedures per day throughout their stay. There is increasing evidence that frequent and repetitive exposure to painful stimuli is associated with poorer outcomes later in life. To date, a wide variety of pain control mechanisms have been developed and implemented to address procedural pain in neonates. This review focused on non-opioid analgesics, specifically non-steroidal anti-inflammatory drugs (NSAIDs) and N-methyl-D-aspartate (NMDA) receptor antagonists, which alleviate pain through inhibiting cellular pathways to achieve analgesia.  The analgesics considered in this review show potential for pain relief in clinical practice; however, an evidence summation compiling the individual drugs they comprise and outlining the benefits and harms of their administration is lacking. We therefore sought to summarize the evidence on the level of pain experienced by neonates both during and following procedures; relevant drug-related adverse events, namely episodes of apnea, desaturation, bradycardia, and hypotension; and the effects of combinations of drugs.  As the field of neonatal procedural pain management is constantly evolving, this review aimed to ascertain the scope of non-opioid analgesics for neonatal procedural pain to provide an overview of the options available to better inform evidence-based clinical practice.  OBJECTIVES: To determine the effects of non-opioid analgesics in neonates (term or preterm) exposed to procedural pain compared to placebo or no drug, non-pharmacological intervention, other analgesics, or different routes of administration.

SEARCH METHODS

We searched the Cochrane Library (CENTRAL), PubMed, Embase, and two trial registries in June 2022. We screened the reference lists of included studies for studies not identified by the database searches.

SELECTION CRITERIA

We included all randomized controlled trials (RCTs), quasi-RCTs, and cluster-RCTs in neonates (term or preterm) undergoing painful procedures comparing NSAIDs and NMDA receptor antagonists to placebo or no drug, non-pharmacological intervention, other analgesics, or different routes of administration.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our main outcomes were pain assessed during the procedure and up to 10 minutes after the procedure with a validated scale; episodes of bradycardia; episodes of apnea; and hypotension requiring medical therapy.

MAIN RESULTS

We included two RCTs involving a total of 269 neonates conducted in Nigeria and India.  NMDA receptor antagonists versus no treatment, placebo, oral sweet solution, or non-pharmacological intervention One RCT evaluated using oral ketamine (10 mg/kg body weight) versus sugar syrup (66.7% w/w at 1 mL/kg body weight) for neonatal circumcision.  The evidence is very uncertain about the effect of ketamine on pain score during the procedure, assessed with the Neonatal Infant Pain Scale (NIPS), compared with placebo (mean difference (MD) -0.95, 95% confidence interval (CI) -1.32 to -0.58; 1 RCT; 145 participants; very low-certainty evidence). No other outcomes of interest were reported on. Head-to-head comparison of different analgesics One RCT evaluated using intravenous fentanyl versus intravenous ketamine during laser photocoagulation for retinopathy of prematurity. Neonates receiving ketamine followed an initial regimen (0.5 mg/kg bolus 1 minute before procedure) or a revised regimen (additional intermittent bolus doses of 0.5 mg/kg every 10 minutes up to a maximum of 2 mg/kg), while those receiving fentanyl followed either an initial regimen (2 μg/kg over 5 minutes, 15 minutes before the procedure, followed by 1 μg/kg/hour as a continuous infusion) or a revised regimen (titration of 0.5 μg/kg/hour every 15 minutes to a maximum of 3 μg/kg/hour). The evidence is very uncertain about the effect of ketamine compared with fentanyl on pain score assessed with the Premature Infant Pain Profile-Revised (PIPP-R) scores during the procedure (MD 0.98, 95% CI 0.75 to 1.20; 1 RCT; 124 participants; very low-certainty evidence); on episodes of apnea occurring during the procedure (risk ratio (RR) 0.31, 95% CI 0.08 to 1.18; risk difference (RD) -0.09, 95% CI -0.19 to 0.00; 1 study; 124 infants; very low-certainty evidence); and on hypotension requiring medical therapy occurring during the procedure (RR 5.53, 95% CI 0.27 to 112.30; RD 0.03, 95% CI -0.03 to 0.10; 1 study; 124 infants; very low-certainty evidence). The included study did not report pain score assessed up to 10 minutes after the procedure or episodes of bradycardia occurring during the procedure. We did not identify any studies comparing NSAIDs versus no treatment, placebo, oral sweet solution, or non-pharmacological intervention or different routes of administration of the same analgesics. We identified three studies awaiting classification.  AUTHORS' CONCLUSIONS: The two small included studies comparing ketamine versus either placebo or fentanyl, with very low-certainty evidence, rendered us unable to draw meaningful conclusions. The evidence is very uncertain about the effect of ketamine on pain score during the procedure compared with placebo or fentanyl. We found no evidence on NSAIDs or studies comparing different routes of administration. Future research should prioritize large studies evaluating non-opioid analgesics in this population. As the studies included in this review suggest potential positive effects of ketamine administration, studies evaluating ketamine are of interest. Furthermore, as we identified no studies on NSAIDs, which are widely used in older infants, or comparing different routes of administration, such studies should be a priority going forward.

Prevalence, frequency, adverse events, and reasons for analgesic use in youth athletes: A systematic review and meta-analysis of 44,381 athletes

OBJECTIVES

To identify the prevalence, frequency, adverse effects, and reasons for analgesic use in youth athletes.

DESIGN

Systematic review and meta-analysis.

METHODS

Systematic searches in Embase, Medline, and SPORT-Discus from inception to September 2021, screening of reference lists, and citation tracking were performed to identify observational studies including athletes aged 15-24 years and reporting data on prevalence and/or frequency of analgesic use. Study quality was assessed using the Newcastle-Ottawa Scale. Random-effect proportion meta-analyses, stratified by type of analgesic medication and prevalence measure, estimated the prevalence of analgesic use. Data on usage frequency, adverse events, and reasons for analgesic use was synthesized narratively.

RESULTS

Forty-nine studies were included (44,381 athletes), of which 19 were good/high quality. Seven categories of analgesics were identified across 10 prevalence time-points. Meta-analyses suggested common use of NSAIDs (point prevalence 48 % [95 % CI 23 % to 73 %], in-season prevalence 92 % [95 % CI 88 % to 95 %]). The lowest prevalence was found for use of local anesthetic injections within the previous 12 months (2 % [95 % CI 1 % to 3 %]). Seven to 50 % of athletes reported weekly analgesics use. The proportion of adverse events ranged from 3.3 % to 19.2 %. Reasons for using analgesics included treatment of sports-related pain or injury, to treat illness, and to enhance performance.

CONCLUSIONS

Analgesics are commonly used in youth athletes, but estimates vary depending on type of analgesic and prevalence measure. As the majority of studies were of poor methodological quality, future high-quality research should include prospective data collection of analgesic use to understand consumption trajectories.

Opioid-Related Genetic Polymorphisms of Cytochrome P450 Enzymes after Total Joint Arthroplasty: A Focus on Drug-Drug-Gene Interaction with Commonly Coprescribed Medications

Pharmacogenomic testing, together with the early detection of drug-drug-gene interactions (DDGI) before initiating opioids, can improve the selection of dosage and reduce the risk of adverse drug interactions and therapeutic failures following Total Joint Arthroplasty. The variants of CYP genes can mediate DDGI. Orthopedic surgeons should become familiar with the genetic aspect of opioid use and abuse, as well as the influence of the patient genetic makeup in opioid selection and response, and polymorphic variants in pain modulation.

Nanomaterials for Photocatalytic Degradations of Analgesic, Mucolytic and Anti-Biotic/Viral/Inflammatory Drugs Widely Used in Controlling SARS-CoV-2

The COVID-19 pandemic has been transformed into one of the main worldwide challenges, in recent years. For controlling symptoms that are caused by this disease (e.g., chills or fever, shortness of breath and/or difficulty in breathing, cough, sore throat, fatigue, headache, muscle aches, the new loss of tastes and/or smells, congestion or runny nose, nausea, vomiting and/or diarrhea), lots of medicines including analgesics, mucolytics, and anti-biotic/viral/inflammatory drugs have been frequently prescribed. As these medicines finally contaminate terrestrial and aquatic habitats by entering surface waterways through pharmaceutical production and excreting trace amounts of waste after human usage, they have negative impacts on wildlife’s health and ecosystem. Residual drugs in water have the potential to harm aquatic creatures and disrupt their food chain as well as the breeding cycle. Therefore, proper degradation of these broadly used medicines is highly crucial. In this work, the use of nanomaterials applicable in photocatalytic degradations of analgesics (e.g., acetaminophen, aspirin, ibuprofen, and naproxen), mucolytics (e.g., ambroxol), antibiotics (e.g., azithromycin and quinolones including hydroxychloroquine and chloroquine phosphate), anti-inflammatory glucocorticoids (e.g., dexamethasone and cortisone acetate), antihistamines (e.g., diphenhydramine), H2 blockers (e.g., famotidine), anthelmintics (e.g., praziquantel), and finally antivirals (e.g., ivermectin, acyclovir, lopinavir/ritonavir, favipiravir, nitazoxanide, and remdesivir) which widely used in controlling/treating the coronavirus have been reviewed and discussed.

Occurrence, detection and ecotoxicity studies of selected pharmaceuticals in aqueous ecosystems- a systematic appraisal

Pharmaceutical compounds (PCs) have globally emerged as a significant group of environmental contaminants due to the constant detection of their residues in the environment. The main scope of this review is to fill the void of information on the knowledge on the African occurrence of selected PCs in environmental matrices in comparison with those outside Africa and their respective toxic actions on both aquatic and non-aquatic biota through ecotoxicity bioassays. To achieve this objective, the study focused on commonly used and detected pharmaceutical drugs (residues). Based on the conducted literature survey, Africa has the highest levels of ciprofloxacin, sulfamethoxazole, lamivudine, acetaminophen, and diclofenac while Europe has the lowest of all these PC residues in her physical environments. For ecotoxicity bioassays, the few data available are mostly on individual groups of pharmaceuticals whereas there is sparsely available data on their combined forms.

Ilex paraguariensis extract as an alternative to pain medications

Pain is a common and distressing symptom of many diseases and its clinical treatment generally involves analgesics and anti-inflammatory drugs. This study evaluated the toxicity of Ilex paraguariensis A. St.-Hil. (Aquifoliaceae) aqueous extract (leaves, petioles and branches) and its performance in a nociceptive response. Hepatotoxicity, psycho-stimulant test and evaluation of enzyme markers for liver damage were also tested. Chromatographic analysis by UPLC-MS demonstrated a series of isomeric monocaffeoylquinic acids, isomers of dicaffeoylquinic acid, flavonol glycosides, and saponins. Phase I and II of nociception were obtained for meloxicam, dexamethasone and aqueous Ilex paraguariensis extract. Ilex paraguariensis extract concentration was negatively correlated (R = -0.887) with alanine aminotransferase (p < 0.05) in acetaminophen-induced hepatotoxicity test, indicating hepatoprotective activity of this extract. Ilex paraguariensis extract also presented analgesic properties equivalent to drugs that already have proven efficacy. Notably, the administration of multiple doses of Ilex paraguariensis extract was considered safe from the therapeutic point of view.

Efficacy and safety of opioid therapy guided by pharmacogenetics: a systematic review

Aim: To perform a systematic review to determine the efficacy/safety of PGx-guided opioid therapy for chronic/postoperative pain. Materials & methods: We searched PubMed and other specialized databases. Articles were considered if they compared the efficacy/safety of PGx-guided opioid therapy versus usual care. The risk of bias assessment was performed using Cochrane tools. Results: A total of 3794 records were retrieved. Only five were included for data extraction. A lower requirement of analgesics during postoperative in the PGx-guided intervention arm was reported in two studies. Also, two studies reported significant pain improvement in favor of the PGx-guided therapy when analyzing the subgroup of patients with a high-risk CYP2D6 phenotype. Conclusion: Despite the findings described, information on the efficacy/safety of this intervention is scarce.

Analgesic and Anti-Inflammatory Effects of Hydroalcoholic and Hexane Extracts of Smyrniopsis aucheri in Animal Models

Background:

The fruits of Apiaceae family have been widely used in traditional medicine for the treatment of pain and inflammation. In this study, we evaluated the analgesic and anti-inflammatory effects of wild celery (Smyrniopsis aucheri) seeds, as a member of the Apiaceae family.

Methods:

Hydroalcoholic and hexane extracts of seeds were prepared and for the evaluation of analgesic activity, acetic acid, formalin, and hotplate tests in male mice (20–30 g) and for anti-inflammatory assessment carrageenan-induced paw edema in rats and croton oil-induced ear edema in mice were used.

Results:

Hydroalcoholic and hexane extracts (100–400 mg/kg) significantly reduced abdominal spasms in the acetic acid test. In the formalin test, the hydroalcoholic extract at doses of 200 and 400 mg/kg reduced the pain of the chronic phase while hexane extract was effective in both acute and chronic phases. In the hot plate test, both extracts were ineffective. In the carrageenan and croton tests, both extracts at a dose of 400 mg/kg significantly reduced edema.

Conclusions:

The results revealed the analgesic and anti-inflammatory effects of plant seed extracts. Due to the lack of response of the extracts in the hot plate test, it seems that the plant mainly has a peripheral analgesic effect.

Pharmacogenomics of Pain Management: The Impact of Specific Biological Polymorphisms on Drugs and Metabolism

PURPOSE OF REVIEW

Pain is multifactorial and complex, often with a genetic component. Pharmacogenomics is a relative new field, which allows for the development of a truly unique and personalized therapeutic approach in the treatment of pain.

RECENT FINDINGS

Until recently, drug mechanisms in humans were determined by testing that drug in a population and calculating response averages. However, some patients will inevitably fall outside of those averages, and it is nearly impossible to predict who those outliers might be. Pharmacogenetics considers a patient's unique genetic information and allows for anticipation of that individual's response to medication. Pharmacogenomic testing is steadily making progress in the management of pain by being able to identify individual differences in the perception of pain and susceptibility and sensitivity to drugs based on genetic markers. This has a huge potential to increase efficacy and reduce the incidence of iatrogenic drug dependence and addiction. The streamlining of relevant polymorphisms of genes encoding receptors, transporters, and drug-metabolizing enzymes influencing the pain phenotype can be an important guide to develop safe new strategies and approaches to personalized pain management. Additionally, some challenges still prevail and preclude adoption of pharmacogenomic testing universally. These include lack of knowledge about pharmacogenomic testing, inadequate standardization of the process of data handling, questionable benefits about the clinical and financial aspects of pharmacogenomic testing-guided therapy, discrepancies in clinical evidence supporting these tests, and doubtful reimbursement of the tests by health insurance agencies.

Molecular Basis of Cancer Pain Management: An Updated Review

Pain can have a significantly negative impact on the quality of life of patients. Therefore, patients may resort to analgesics to relieve the pain. The struggle to manage pain in cancer patients effectively and safely has long been an issue in medicine. Analgesics are the mainstay treatment for pain management as they act through various methods on the peripheral and central pain pathways. However, the variability in the patient genotypes may influence a drug response and adverse drug effects that follow through. This review summarizes the observed effects of analgesics on UDP-glucuronosyl (UGT) 2B7 isoenzyme, cytochrome P450 (CYP) 2D6, μ-opioid receptor μ 1 (OPRM1), efflux transporter P-glycoprotein (P-gp) and ATP-binding cassette B1 ABCB1/multiple drug resistance 1 (MDR1) polymorphisms on the mechanism of action of these drugs in managing pain in cancer. Furthermore, this review article also discusses the responses and adverse effects caused by analgesic drugs in cancer pain management, due to the inter-individual variability in their genomes.

Could Mycolactone Inspire New Potent Analgesics? Perspectives and Pitfalls

Pain currently represents the most common symptom for which medical attention is sought by patients. The available treatments have limited effectiveness and significant side-effects. In addition, most often, the duration of analgesia is short. Today, the handling of pain remains a major challenge. One promising alternative for the discovery of novel potent analgesics is to take inspiration from Mother Nature; in this context, the detailed investigation of the intriguing analgesia implemented in Buruli ulcer, an infectious disease caused by the bacterium Mycobacterium ulcerans and characterized by painless ulcerative lesions, seems particularly promising. More precisely, in this disease, the painless skin ulcers are caused by mycolactone, a polyketide lactone exotoxin. In fact, mycolactone exerts a wide range of effects on the host, besides being responsible for analgesia, as it has been shown notably to modulate the immune response or to provoke apoptosis. Several cellular mechanisms and different targets have been proposed to account for the analgesic effect of the toxin, such as nerve degeneration, the inhibition of inflammatory mediators and the activation of angiotensin II receptor 2. In this review, we discuss the current knowledge in the field, highlighting possible controversies. We first discuss the different pain-mimicking experimental models that were used to study the effect of mycolactone. We then detail the different variants of mycolactone that were used in such models. Overall, based on the results and the discussions, we conclude that the development of mycolactone-derived molecules can represent very promising perspectives for new analgesic drugs, which could be effective for specific pain indications.

Pharmacogenetic Testing in Acute and Chronic Pain: A Preliminary Study

Background and Objectives: Pain is one of the most common symptoms that weighs on life’s quality and health expenditure. In a reality where increasingly personalized therapies are needed, the early use of genetic tests that highlights the individual response to analgesic drugs could be a valuable help in clinical practice. The aim of this preliminary study is to observe if the therapy set to 5 patients suffering of chronic or acute pain is concordant to the Pharmacogenetic test (PGT) results. Materials and Methods: This preliminary study compares the genetic results of pharmacological effectiveness and tolerability analyzed by the genetic test Neurofarmagen Analgesia^®, with the results obtained in clinical practice of 5 patients suffering from acute and chronic pain. Results: Regarding the genetic results of the 5 samples analyzed, 2 reports were found to be completely comparable with the evidences of the clinical practice, while in 3 reports the profile of tolerability and effectiveness were partially discordant. Conclusion: In light of the data not completely overlapping with results observed in clinical practice, further studies would be appropriate in order to acquire more information on the use of Neurofarmagen in routine clinical settings.

Mycolactone as Analgesic: Subcutaneous Bioavailability Parameters

Mycobacterium ulcerans is the bacillus responsible for Buruli ulcer, an infectious disease and the third most important mycobacterial disease worldwide, after tuberculosis and leprosy. M. ulcerans infection is a type of panniculitis beginning mostly with a nodule or an oedema, which can progress to large ulcerative lesions. The lesions are caused by mycolactone, the polyketide toxin of M. ulcerans. Mycolactone plays a central role for host colonization as it has immunomodulatory and analgesic effects. On one hand, mycolactone induces analgesia by targeting type-2 angiotensin II receptors (AT₂R), causing cellular hyperpolarization and neuron desensitization. Indeed, a single subcutaneous injection of mycolactone into the mouse footpad induces a long-lasting hypoesthesia up to 48 h. It was suggested that the long-lasting hypoesthesia may result from the persistence of a significant amount of mycolactone locally following its injection, which could be probably due to its slow elimination from tissues. To verify this hypothesis, we investigated the correlation between hypoesthesia and mycolactone bioavailability directly at the tissue level. Various quantities of mycolactone were then injected in mouse tissue and hypoesthesia was recorded with nociception assays over a period of 48 h. The hypoesthesia was maximal 6 h after the injection of 4 μg mycolactone. The basal state was reached 48 h after injection, which demonstrated the absence of nerve damage. Surprisingly, mycolactone levels decreased strongly during the first hours with a reduction of 70 and 90% after 4 and 10 h, respectively. Also, mycolactone did not diffuse in neighboring skin tissue and only poorly into the bloodstream upon direct injection. Nevertheless, the remaining amount was sufficient to induce hypoesthesia during 24 h. Our results thus demonstrate that intact mycolactone is rapidly eliminated and that very small amounts of mycolactone are sufficient to induce hypoesthesia. Taken together, our study points out that mycolactone ought to be considered as a promising analgesic.

Renal impairment and analgesia: From effectiveness to adverse effects

Kidney pain is one of the clinically significant features of renal dysfunction. Mild to severe pain is seen in the lower back area. Painkillers are mostly recommended in these cases to relieve the symptom. Yet, several analgesics are associated with side effects that can worsen the state of the disease. This review is based on the studies conducted in these aspects analgesics used to treat kidney pain and their effectiveness, renal consequences of postoperative analgesia, and pharmacogenetics of these palliatives are briefly summarized in this paper.

The management of post-traumatic stress disorder and associated pain and sleep disturbance in refugees

More than 68 million people worldwide have been forcibly displaced and one-third of these are refugees. This article offers an overview of the current literature and reviews the epidemiology and evidence-based psychological and pharmacological management of post-traumatic stress disorder (PTSD), sleep disturbance and pain in refugees and asylum seekers. It also considers the relationship between sleep disturbance and PTSD and explores concepts of pain in relation to physical and psychological trauma and distress. During diagnosis, clinicians must be aware of ethnic variation in the somatic expression of distress. Treatments for PTSD, pain and sleep disturbance among refugees and asylum seekers are essentially the same as those used in the general population, but treatment strategies must allow for cultural and contextual factors, including language barriers, loss of freedom and threat of repatriation.

LEARNING OBJECTIVES

After reading this article you will be able to: •

DECLARATION OF INTEREST

None.

Effects of Single Nucleotide Polymorphisms on Surgical and Postsurgical Opioid Requirements: A Systematic Review and Meta-Analysis

OBJECTIVES

There is great heterogeneity in the way individuals respond to medications. Inherited differences, such as single nucleotide polymorphisms (SNP), can influence the efficacy and toxicity of drugs. This meta-analysis aims to collate data from studies investigating the effect of SNPs on postoperative and/or intraoperative opioid requirements.

MATERIALS AND METHODS

A meta-analysis was conducted following PRISMA guidelines. Eligibility criteria for studies included were reporting amount of postoperative and/or intraoperative opioid used as the primary outcome and genotyping patients for SNPs in one of the following genes; OPRM1, CYP2D6, CYP3A4, CYP3A5, COMT, UGT2B7, or ABCB1. A comprehensive systematic search for articles using keywords "opioid-sensitivity," "polymorphisms," "post-operative opioid," "post-surgical opioid," "post-operative pain," and "post-surgical pain" was performed.

RESULTS

Fifty-one studies were included. Individuals homozygous for AA at the OPRMI (rs1799971) polymorphisms required less postsurgical opioid compared with those homozygous for GG (Hedges g, -0.270; 95% confidence interval, -0.433 to -0.108; P=0.001). Polymorphisms in CYP2D6, CYP3A4, CYP3A5, COMT, UGT2B7, and ABCB1 did not affect opioid requirements.

DISCUSSION

Investigation of single changes in 1 gene can only yield limited information regarding genetic effects on opioid requirements. Rapid development of whole genome sequencing enables information on all genetic modifications that may affect analgesic response to be collected. The information collected must include data on the individual's metabolic enzymes, as well as information on drug receptors and enzymes responsible for drug degradation, so that a personal profile can be built up which will predict individual response to drugs, and guide clinicians on the type and dosage of drug to use.

Pupillary Unrest in Ambient Light and Prediction of Opioid Responsiveness: Case Report on Its Utility in the Management of 2 Patients With Challenging Acute Pain Conditions

Pupillary unrest in ambient light (PUAL), the normal pattern of pupil diameter fluctuation present in awake humans, has been proposed as a marker of central opioid effect. We report 2 cases in which PUAL identified the appropriate pain management for 2 patients, each with unique, challenging acute pain conditions. In both cases, PUAL accurately predicted opioid responsiveness, suggesting an effective, individualized analgesic approach for both patients.

Pharmacogenetics of Opioid Use and Implications for Pain Management

BACKGROUND

Opioid analgesics are frequently prescribed to manage acute and chronic pain, but individual differences in opioid response make effective pain control in all patients an elusive goal. Furthermore, the risk of addiction following opioid consumption varies among individual patients. Although many psychosocial factors contribute to an individual's opioid response and risk for addiction, a strong genetic component has also been demonstrated.

CONTENT

Opioids undergo substantial enzymatic modification that can generate metabolites with either increased or decreased opioid activity relative to the parent compound. To elicit their analgesic effect, parent compounds and active metabolites must be transported into the central nervous system where they bind to opioid receptors and inhibit neurotransmission. Inherited genetic variants that alter the function of proteins involved in these processes have been associated with differences in opioid response and risk for addiction. Detection of these variants can help guide opioid selection, inform dosing decisions, or encourage use of a nonopioid analgesic.

SUMMARY

Whereas some genetic variants are clearly associated with differences in opioid response and have been included in consensus clinical practice guidelines, the impact of other variants on opioid response remains unclear. Studies performed to date have generated promising results, but inconsistent findings, reimbursement challenges, and the lack of robust decision support tools have hampered widespread adoption of pharmacogenetic testing to guide pain management treatment decisions. Future work involving the simultaneous evaluation of large numbers of variants and demonstration of a clear clinical benefit provided by pharmacogenetic testing will be required to overcome these obstacles.

Point-of-care companion diagnostic tests for personalizing psychiatric medications: fulfilling an unmet clinical need

Over the last decade stable isotope-labeled substrates have been used as probes for rapid, point-of-care, non-invasive and user-friendly phenotype breath tests to evaluate activity of drug metabolizing enzymes. These diagnostic breath tests can potentially be used as companion diagnostics by physicians to personalize medications, especially psychiatric drugs with narrow therapeutic windows, to monitor the progress of disease severity, medication efficacy and to study in vivo the pharmacokinetics of xenobiotics. Several genotype tests have been approved by the FDA over the last 15 years for both cytochrome P450 2D6 and 2C19 enzymes, however they have not been cleared for use in personalizing medications since they fall woefully short in identifying all non-responders to drugs, especially for the CYP450 enzymes. CYP2D6 and CYP2C19 are among the most extensively studied drug metabolizing enzymes, involved in the metabolism of approximately 30% of FDA-approved drugs in clinical use, associated with large individual differences in medication efficacy or tolerability essentially due to phenoconversion. The development and commercialization via FDA approval of the non-invasive, rapid (<60 min), in vivo, phenotype diagnostic breath tests to evaluate polymorphic CYP2D6 and CYP2C19 enzyme activity by measuring exhaled ¹³CO₂ as a biomarker in breath will effectively resolve the currently unmet clinical need for individualized psychiatric drug therapy. Clinicians could personalize treatment options for patients based on the CYP2D6 and CYP2C19 phenotype by selecting the optimal medication at the right initial and subsequent maintenance dose for the desired clinical outcome (i.e. greatest efficacy and minimal side effects).

Managing interactions between cognitive enhancers and other psychotropics

Polypharmacy is common in psychiatry. Usage of cognitive enhancers is increasing in the psychiatric population. Many clinicians are not familiar with these new psychoactive compounds. This paper reviews the potential drug-drug interactions when these cognitive enhancers are used together with psychotropic drugs and their confounding effects on diagnosis and clinical management.

Pharmacogenomics in Anesthesia

A significant number of commonly administered medications in anesthesia show wide clinical interpatient variability. Some of these include neuromuscular blockers, opioids, local anesthetics, and inhalation anesthetics. Individual genetic makeup may account for and predict cardiovascular outcomes after cardiac surgery. These interactions can manifest at any point in the perioperative period and may also only affect a specific system. A better understanding of pharmacogenomics will allow for more individually tailored anesthetics and may ultimately lead to better outcomes, decreased hospital stays, and improved patient satisfaction.

Pharmacogenomics in Pain Management

There is interpatient variability to analgesic administration. Much can be traced to pharmacogenomics variations between individuals. Certain ethnicities are more prone to reduced function of CYP2D6. Weak opioids are subject to interpatient variation based on their CYP2D6 type. Strong opioids have variations based on their transport and individual metabolism. Several cytochrome enzymes have been found to be involved with ketamine but there is no strong evidence of individual polymorphisms manifesting in clinical outcomes. Nonsteroidal anti-inflammatory drugs have adverse outcomes that certain CYP variants are more prone toward. There are now recommendations for dosing based on specific genomic makeup.

Clinical pharmacology of analgosedatives in neonates: ways to improve their safe and effective use

OBJECTIVES

To propose approaches tailored to the specific needs of neonates, such as structured product development programmes, with the ultimate goal to improve the safe and effective use of analgosedatives in these fragile patients.

KEY FINDINGS

The feasibility and relevance of a structured product development programme in neonates (optimal study design based on preliminary data; model development; internal, external and prospective evaluation; an individualized dosing regimen; long-term safety; pharmacogenetics) are illustrated for the use of morphine. Based on changes in clinical practices, similar development plans are in progress for short-acting analgosedatives such as propofol, but are in need of tailored pharmacodynamic tools to assess and quantify effects. Furthermore, for drugs like paracetamol where there is already sufficient clinical pharmacology knowledge, attention needs to be given to long-term safety aspects. Finally, new covariates such as pharmacogenetics might further improve neonatal pain management, but clearly need to be integrated with other well-established covariates like age or weight.

SUMMARY

Product development programmes for analgosedatives in neonates are needed. These programmes should be tailored to their specific needs (short-acting sedation, pain relief), should include long-term safety and should incorporate the exploration of newer covariates like pharmacogenetics.

Splice variation of the mu-opioid receptor and its effect on the action of opioids

An individual's response to opioids is influenced by a complex combination of genetic, molecular and phenotypic factors.Intra- and inter-individual variations in response to mu opioids have led to the suggestion that mu-opioid receptor subtypes exist.Scientists have now proven that mu-opioid receptor subtypes exist and that they occur through a mechanism promoting protein diversity, called alternative splicing.The ability of mu opioids to differentially activate splice variants may explain some of the clinical differences observed between mu opioids.This article examines how differential activation of splice variants by mu opioids occurs through alternative mu-opioid receptor binding, through differential receptor activation, and as a result of the distinct distribution of variants located regionally and at the cellular level.

Pharmacogenetics of chronic pain management

OBJECTIVE

The experience of chronic pain is one of the commonest reasons individuals seek medical attention, making the management of chronic pain a major issue in clinical practice. Drug metabolism and responses are affected by many factors, with genetic variations offering only a partial explanation of an individual's response. There is a paucity of evidence for the benefits of pharmacogenetic testing in the context of pain management.

DESIGN AND METHODS

We reviewed the literature between 2000 and 2013, and references cited therein, using various keywords related to pain management, pharmacology and pharmacogenetics.

RESULTS

Opioids continue to be the mainstay of chronic pain management. Several non-opioid based therapies, such as treatment with cannabinoids, gene therapy and epigenetic-based approaches are now available for these patients. Adjuvant therapies with antidepressants, benzodiazepines or anticonvulsants can also be useful in managing pain. Currently, laboratory monitoring of pain management patients, if performed, is largely through urine drug measurements.

CONCLUSIONS

Drug half-life calculations can be used as functional markers of the cumulative effect of pharmacogenetics and drug-drug interactions. Assessment of half-life and therapeutic effects may be more useful than genetic testing in preventing adverse drug reactions to pain medications, while ensuring effective analgesia. Definitive, mass spectrometry-based methods, capable of measuring parent drug and metabolite levels, are the most useful assays for this purpose. Urine drug measurements do not necessarily correlate with serum drug concentrations or therapeutic effects. Therefore, they are limited in their use in monitoring efficacy and toxicity.